Fungicides are registered and labeled for agricultural use only after numerous trials and years of testing and disease evaluations that demonstrate the activity of the product. In California and in some other states, efficacy data has to be submitted as part of the registration process. Most fungicides perform generally well under environmental conditions that occur in California. Still, their performance is dependent on many factors including physical and chemical properties of the fungicide, as well as the environmental and biological conditions in the agricultural system where they are used. Factors including deposition (e.g., application methods, rates, intervals, and coverage of plant surfaces) and depletion (rate of degradation from water, sunlight, microbial enzymatic breakdown, volatilization, systemic action, plant growth, etc.) will determine the persistence of fungicides on plant surfaces and contribute to the overall performance.
The disease triangle (the interaction between host, pathogen, and environment) determines the disease pressure in any agro-system. Susceptibility of plant cultivars and the conduciveness of environmental conditions before, during, and after fungicide application will affect disease development and ultimately, the performance of the fungicide. Furthermore, the sensitivity of the pathogen to the fungicide may change or “shift” with usage over time through adaptation or genetic resistance and thus, this greatly influences the success or failure of any fungicide product used under field conditions.
In this document, we rated the performance of conventional fungicides and bactericides, biocontrols, and natural products for managing major diseases caused by fungi and bacteria of temperate fruit (pome and stone fruit) and nut tree (almond, pistachio, and walnut) crops, citrus, grapevines, and strawberries that are major fruit and nut crops in California. For each product, the mode of action is shown and is based on the Fungicide Resistance Action Committee or FRAC Codes. A complete listing of the FRAC codes can be found at: https://www.frac.info/knowledge-database/downloads.
Performance ratings of products listed are based on direct experience from research trials evaluating the performance of the tested products under field conditions. Environmental conditions and pathogen populations may greatly influence the performance of the materials. A numbering system denotes:“0” = ineffective; “1” = minimal and often ineffective; “2” = limited and erratic; “3” = moderate and sometimes variable; “4” good and reliable; and “5” = excellent and consistent. Generally, “4” and “5” are commercially acceptable. Ratings with “1”, “2”, or “3” represent variability in performance inversely related to pathogen population, favorable environments, or host susceptibility. Thus, the performance ratings are relative in comparison to other products and may change as experience is gained in using the individual products. Attributes or deficiencies of a product are noted where information is available. For example, the resistance potential (presence of resistant pathogen populations in California) and persistence or degradation rate is cited for individual products when this information is known. Most materials are labeled for the management of the diseases for which ratings are presented. However, some products have been tested but are not labeled for managing a specific disease. Always consult the product label to ensure that the fungicide is currently registered for a specific use. This document is not a legal recommendation for using pesticides. When using pesticides, always consult with licensed pest control advisors or qualified pesticide applicators.